Drive axle and track frame mounting for crawler tractors



March 4, 1952 w. F. WILSON 2,588,333

DRIVE1 AXLE AND TRACK FRAME MOUNTING FOR CRAWLER TRACTORS Filed March 5, 1947 5 Sheets-Sheet l ATTORNEY March 4, 1952 W. F. WILSON DRIVE AXLE AND TRACK FRAME MOUNTING FOR CRAWLER TRACTORS 3 Sheets-Sheet 2 Filed March 3, 1947 March 4, 1952 w. F. WILSON DRIVE AXLE AND TRACK FRAME MOUNTING FOR CRAWLER TRACTORS 5 Sheets-Sheet 3 Filed March 3, 1947 ORNEY Patented Mar. 4, 1952 DRIVE AXLE AND TRACK FRAME MOUNTING FOR CRAWLER TRACTORS William F. Wilson, Wauwatosa, Wis., assigner to Allis-Chalmers Manufacturing Company, M11- waukee, Wis., a corporation of Delaware `Application March 3, 1947, Serial No. 732,029

3 Claims.

The invention relates to motor vehicles, and it is concerned more particularly with an improved drive axle and track frame mounting for crawler tractors.

In the construction of crawler tractors as disclosed, for instance, in U. S. Patent` 1,968,419, granted on July 31, 1934, to E. F Norelius for Transmission Mechanism, it has heretofore been a common practice to mount the track belt drive sprockets in overhanging relation to the main body of the tractor at opposite sides and at the rear of the latter, and to transmit driving power to these sprockets through nal drive gears, that is, through individual speed reducing gear trains at opposite sides, respectively, of the tractor. A large, walled structure which forms the rear part of the main body and which serves as a transmission housing is usually employed to mount the iinal drive gears and other mechanism, such as a pair of steering clutches, a common drive shaft for the latter, and a bevel gear and pinion drive for transmitting power to the drive shaft of the steering clutches.

While all of the mentioned power transmitting mechanism is amply proportioned to handle the available engine power, its ability to do so efiiciently and without interruption during long periods of operation, is usually dependent upon refinements of construction, as is well known in the art. For instance, certain critical dimensions which determine the relative position of the cooperating elements of each nal drive gear train must be maintained within very close limits in order to insure eiiicient and trouble-free opera-V tion of said gears under heavy loads. And simi- 1ar1y,the efficiency and satisfactory operation of` certain oil seals which are employed to retain lubricant in the transmission housing are usually dependent upon a highly accurate relation of the cooperating parts thereof.

According to established usage, the transmission; housing, in addition to serving as a support for the track belt drive sprockets, nal drive gearings and associated power transmitting mechanism, also constitutes that part of the main body of the tractor on which the track frames are mounted for pivotal up and down movement independently of each other. In order to provide the required pivotal mountings for the track frames at opposite sides of the main body, it has heretofore been customary to secure a one-piece axle or a pair of alined stub-axles, as shown in the hereinabove mentioned Norelius patent, in rigid, non-rotatable relation tothe transmission housing, and to pivot the track. frames at their rear ends on overhanging portions of such dead axle or axles. While the primary purpose of such an arrangement is to support the main body at its rear end on the track frames, the loads resulting from the Weight of the main body are usually not the only ones Which are intended to be transmitted from the main body to the track frames,` and vice versa, through the mentioned dead axle or axles. The track frames must be stabilized against toeing in and out and against lateral tilting relative to the main body, and arrangements involving the dead. axle or axles to provide for the necessary horizontal and vertical stability of the track frames are quite common. Moreover, it is usual to connect certain types of tractor operated equipment, particularly bulldozers, in thrust transmitting relation directly to the track frames rather than to the main body of the tractor, and it is apparent that under these conditions the dead axle or axles, as well as the transmission housingare apt to become most severely stressed during operation of the tractor.

During the past, it has been found extremely difficult in tractors of the hereinabove outlined character, to prevent the normally heavy, and

under certain conditions extremely severe loads to which the transmission housing becomes subjected, from upsetting the highly accurate relation between the cooperating elements of the iinal drive gear trains and other parts, and which accurate relation is required, as pointed out hereinbefore, for eiicient and trouble-free operation of the tractor. Failure of the nal drive gears has been one of the most persistent troubles in crawler tractors as heretofore constructed, and various attempts have been made, as evidenced for instance by U. S. Patent 2,391,001, granted on December 18, 1945, to D. B. Baker et al., and by U. S. Patent 2,453,360, granted on November 9, 1948, to G. E. Burks, to avoid relative displacement of the final drive gears, and consequent undue stresses and ultimate failure of these gears under heavy loads.

Generally, it is an object of the invention to provide an improved drive axle and track frame mounting which will overcome the hereinabove outlined ditliculties in a practical and fully satisfactory manner.

More specically, it is an object of the invention to provide an improved drive axle and track` frame arrangement which will efficiently func-V tion to transmit power to the track belt drive sprockets, which will insure proper stability ofi the track frames against toeing in and out and against lateral tilting, and in which the cooperative relation between the elements of the final drive gear trains will not be adversely affected by heavy loads to which the track frames may become subjected under severe operating conditions of the tractor, as during steering or bulldozing.

A further object of the invention is to provide an improved drive axle and track frame arrangement of the character set forth hereinbefore, in which Vrotary shaft seals for retaining aA lubricant supply in an enclosure for the final drive gears are of relatively small diameter.

A further object of the invention is to provide an improved drive axle and track frame mounting which will satisfactorily take care of the load conditions which arise when the track belt tension is increased beyond normal, as for instance when a stone or other solid obstruction becomes lodged on one of the track belts and is forced to pass with the latter around the respective track belt drive sprocket, the improved mounting being such that the transmission housing and the bearings for the track belt drive sprockets will not become subject to objectionable or harmful stresses under said conditions, that is,'to stresses which would disturb the proper mesh and load distribution of the final drive gears.

A further object of the invention is to provide an improved crawler type tractor of the threepoint suspension type, in which the transverse pivot axis about which the track frames are swingable up and down independently of each other, coincides with the axis of rotation of the track belt drive sprockets, and in which the nal drive gears and the oil seals associated with the transmission housing will reliably function without undue wear or failure during long periods of service under the most punishing operating conditions.

A further object of the invention is to provide an improved crawler type tractor of the character set forth hereinbefore, in which the track belt drive sprocket and the track frame, at each side ofthe tractor, cooperate to relieve the mounting of the track belt drive sprockets on the transmission housing from undue stresses under certain operating conditions, as during steering or bulldozing.

A still further object of the invention is to provide an improved crawler tractor of the character set forth hereinabove, in which inboard and outboard pivot bearings for the track frames are mounted on the main body at a desirable transverse spacing from each other, which will provide satisfactory stability of the track frames against toeing in and out and against lateral tilting.

These and other objects and advantagesare attained by the present invention, various novel features of which will be apparent from the description herein and accompanying drawings disclosing an embodiment of the invention, and will be more particularly pointed out in the appended claims.

vIn the drawings:

Fig. 1 is a side view of a crawler tractor;

Y Fig. 2 is a sectional view, at an enlarged scale, on line II-II of Fig. 1;

Figs. 3 and 4 areschematic top and rear views, respectively, outlining in general the tractor shown in Fig. 1, portions of a bulldozer attachment being indicated in dash-dotted lines in Fig. 3;

Fig. 5 is an enlarged rear view of part of the rear housing structure of the tractor shown in Figs. 1, 3 and 4;

Fig. 6 is a side view of the housing part shown in Fig. 5;

Fig. '1 is a sectional view on line VII-VII of Fig. 5,'

Fig. 8 is an enlarged side view of an outboard bearing at the side of the tractor shown in Fig. 1, the view of Fig. 8 being taken in the direction of arrow VIII in Fig. 4;

Fig. 9 is a detail view, in section, of a mounting bracket for a bulldozer, indicated in dashdotted lines in Fig. 3; and

Fig. 10 is a force diagram.

Features of the herein disclosed crawler tractor, and more particularly of the track frame mounting shown in Figs. 3 and 4 hereof, are claimed in a copending application Serial No. 735,195, filed March 11, 1947, by Frederick A. Schick for Track Frame Mounting for Crawler Tractors.

The tractor shown in Figs. 1, 3 and 4 is of the three-point suspension type and comprises a main body generally indicated by the reference character I in Fig. 3, and two self-laying track units at opposite sides, respectively, of the main body, the frame of the self-laying track unit at the lleft side of the main bodybeing generally indicated in Fig. 3, by the reference character 2, and the frame of the self-laying track unit at the right side of the main body being generally indicated in the same gure by the reference character 3.

Referring to Fig. 1, an internal combustion engine 4 is mounted on a frame structure 6 of the main body I in the usual forward position, and the frame structure 6 is rigidly secured at transversely spaced rearward portions thereof to a transmission housing which is generally indicated by the reference character 1 and which forms the rear part of the main body A radiator and shell assembly 8, a hood 9, a dashboard II, controls I2, an o-perators seat I3 and a fuel tank I4 are mounted on the main body in conventional manner.

The transmission housing 1, is shown in the drawings as being constructed in the form of a fabricated structure which comprises a welded assembly of a number ofk plate or sheet steel members, but for the purposes of the present invention thetransmission housing could be constructed,A if desired, in the form of a casting. Generally, the transmission housing 1 is an integral structure which, as shown in Fig. 4, is internally partitioned to provide, a central wet compartment I6 for a bevel gear and pinion drive I1, two dry compartments I8 and I9 for steering clutches 2| and 22, respectively, and two wet Vnal drive gear compartments 23 and 24. A pair of vertically disposed and transversely spaced intermediate walls 2B and 21 of thetransmission housing are connected bytop and bottom walls 28 and 29, as shown in Fig. 4, and vertically disposed front and rear walls 3| and 32, generally indicated in Figs. 3, 6 and '1, extend betionedwet compartment I6 and into the two dry compartments I8 and I9. The bevel gear and pinion drive I1 forms part of a conventional mechanism for transmitting power from the er1- gine 4 vto the steering clutches 2| and 22, a common drive shaft 36 for the two steering clutches ment has been omitted in Fig. 3 in' order to clarify details of the track frame mounting which will be discussed hereinbelow. The top wall 28 of the transmission housing has a suitable center opening 20, and lateral openings 3l), as indicated in Figs. 5, 6 and 7, which afford the necessary access to thebevel gear compartment I6, and to the Asteering clutch compartments I8 and i9, respectively, for assembly purposes, and which are normally closed by covers (not shown) in conformity with usual practice.

Referring to Figs. and 6, the intermediate wall 26 of the transmission housing 1 extends below the bottom wall 29 and has a straight horizontal bottom edge portion 31, a forwardly and upwardly inclined front edge portion 38, vertical front and rear edge portions 39 and 4l, and a horizontal top edge 42. A rectangular boss 43 below the bottom wall 29 and adjacent to the inner side of the depending portion of the wall 28 (Fig. 5) is welded to the latter and to the bottom wall 29. Also welded to the wall 26, at the outer side thereof and in axial alinement with the clutch driving shaft 36, is an annular boss 44, and another annular boss 45 is likewise welded to the outer side of the wall 2t in forwardly and downwardly offset relationA to the boss 44.

A curved plate metal member 4'! (Fig. 6) which forms a continuous top, front and bottom wall of the iinalvdrive gear compartment 23 at the left side of the transmissionhousing is set on edge against a contiguous portion of the wall 25 and is secured thereto by welding, a portion of the wall member 41 adjacent to the wall 23 being cut out to accommodate the boss 44. The config uration of the circumferential wall 41 is such as to provide spaces of dierent transverse width within the final drive gear compartment 23, namely, a space of maximum transverse width in the central region, a space of reduced transverse width in the upper region, and another space of reduced transverse width in the lower region below the bottom edge 31 of the wall 25. The space of reduced width in the upper regionis bounded by a dome shaped upper portion of the circumferential wall member 41 and by a substantially triangular end plate 48 which is welded along div-erging upper edge portions thereof to the edge of the mentioned dome shaped upper portion of the wall member 41 in parallel and transversely spaced relation to the wall 26.

` The space of maximum width in the central region of the nal drive gear compartment 23 and the space 0f reduced width in the lower re g'ion thereof are bounded by a generally arcuate, downwardly and rearwardly extending portion of the wall member 41, and by an end plate 43 which has a zigzag top edge 5l, a straight rear edge adjacent to a transverse plane through the vertical rear edge 4l of the wall 26, and continuous front and bottom edge portions conforming with the generally arcuate, downwardly and rearwardly extending portion of the wall member 41. and bottom edge portions to adjacent edge p0rtions of the wall member 41 in parallel and trans- 'versely spaced relation to the wall 26. A zigzag The end plate 49 is welded along its front shaped filler strip 52 is welded along its opposite longitudinal edges to the zigzag top edge 5| of the end plate 49 and to a corresponding zigzag bottom edge of the triangular end plate 48 to close the transverse gap between Lthe two end plates 48 'and 49, the forward edge of the filler strip 52 being welded to a transverse edge portion 50 (Fig. 6) of the wall member 41. i

The space of maximum width in the central region of the nal drive gear compartment23 is further bounded by a rectangular, horizontal bottom plate 53 which is welded along its inner longitudinal edge to the straight bottom edge 31 of the wall 25, and along its front edge to` a transverse edge portion 55 (Fig. 6) of the wall member 41. A vertical closure plate 54 has a straight horizontal top edge abutting the bottom plate 53, a straight rear edge in the same transverse plane as the rear edge of the end plate 49, and a continuous front and bottom edge conforming to the conguration of the lower portion of the wall member 41. The closure plate 54 is secured in place by welding along its top edge to the bottom plate 53, and along its front and bottom edge to the wall member 41.

A relatively heavy, apertured back plate 56 is arranged in vertical position at the rear side of the nal drive compartment 23, in laterally abutting relation to the wall 25 and in .forwardly abutting relation to the rear edges of the wall member 41, end plate 43, iiller strip 52, bottom plate 53 and closure plate 54, the back plate 56 being united with these members by welding all around the edges thereof contiguous tothe back plate.

rI'he triangular end plate 48 and the end plate 49 together with the filler strip 52 form an end wall of the transmission housing 1, at the left side of the latter, and it will be noted that the intermediate wall 26 of said housing is integrally connected with said end wall in transversely spaced relation thereto, through the wall member 41, plates 53, 54 and 55 and the associated welded connections.

Referring to Fig. 2, a pinion shaft 51 is connected in driven relation with the driven member of the steering clutch 2| at the left side of the tractor, the shaft 51 being axially alined with the driving shaft 36 shown'in Fig. 4. The annular boss 44 which, as stated hereinbefore, is welded to the outer side of th-e housing wall 25, has a central bore for the reception of the outer race of a conical roller bearing 581, and the boss 44 has a counter bore adjacent to and reg istering with a bor-e in the wall 26 for the reception of a bearing and seal retainer 55 which is secured in pla-ce by cap screws 6| The inner race of the roller bearing 58 is fitted upon an intermediate portion of the shaft 51, and a driven head section 62 of the steering clutch 2l is fitted upon a tapered, splined portion 60 of the shaft 51 at the right side of the bearing 58, the head section 62 being secured against axial withdrawal from the shaft 51 in conventional manner by a cap screw 63 and washer 64. An oil seal B6 of conventional construction, for instance of the leather cuff and garter spring type is operatively interposed between the hub of the head section 62 and the retainer 59 to prevent the passage of lubricant from the final drive gear compartment 23 into the clutch compartment I3.

The pinion shaft 51 is rotatably supported at itsaxially outer end by means of a conical roller bearing 61 which is fitted into a bore of the triangular plate 43 and into a registering bore of.

a ring V68 which is weldedto the outside of the plate 48 above the filler strip 52. A retainer and closure cap 09 for the roller bearing 01 is secured to the ring 08 by cap screws 1|.

Integrally formedv with the pinion shaft 51 in the space between the roller bearings 58 and 01 is a spur gear pinion 12 which meshes with a spur gear 13, and which latter gear forms part of an intermediate gear cluster of the final drive gear train in the compartment 23 of the transmission housing 1. The spur gear 13 has-a splined central aperture for the reception of an arbor 14 which has opposite trunnions within conical roller bearings Yand 11. The internal splines of the spur gear 'I3 engage externalsplines 15 of the arbor 14, and the spur gear 13 is secured against axial displacement relative to the arbor 14 by means of arcuate retainers 18 which are secured to the hub of the spur gear 13 by cap screws 19 and engage a-circumferential groove of the arbor 14. The outer race of the conical roller bearing 10 is seated in a bore of the annular boss which, as stated, is welded to the outside of the wall 20, `a portion of the bore in the boss 40 being reduced in diameter to provide a shoulder for axial engagement by the outer race of the rollei` bearing 15.

The outer race ofthe bearing 11 is fitted into a bearing cap 8|Y which has a cylindrical portion seated in a bore of the end plate 49 and in the registering bore of a ring 82 which is welded to the outside of the end plate 49. A series of cap screws 83 extend through a flange of the cap 8i into tapped holes of the ring 82 and are drawn up to secure the roller bearings 110 and 11 in axially adjusted position.

Integrally formed with the arbor 14, at the left side of the spur gear 13, is a spur gear pinion 84 of. substantially smaller pitch diameter than the pitch diameter of the spur gear 13. A large diameter spur gear 89 which meshes with the pinion. 84, is mounted on a shaft 91 which constitutes one of a pair of live axles at opposite sides, respectively, of the tractor. As shown in Fig. 2, the shaft or live axle 81 at the left side of the tractor is rotatably supported on the transmission housing 'l' by means of two conical roller bearings 89 and 8,9. The roller bearing 88 which supports the shaft 81 at its axially inner end is seated in registering bores of the intermediate wall 20 and of the rectangular boss 43. The roller bearing 89 supports the shaft 81 on the transmission housing 1 at a portion of the shaft substantially midway between its ends. A ring 9| of substantially U-shaped cross-section is seated at the edge of its outer circumferential wall over a large opening in the end plate 49, and the ring 9| is secured to said plate by an outer circumferential weld along said edge. The inner wall of the ring; 9| has an axially extending cylindrical surface of a diameter to permit insertion of the outer race of the roller bearing 89 into the ring 9| under relatively light axial pressure. The inner race of the bearing 89 bears against a shoulder 92 of the shaft 81, and a bearing retainer 93 for the outer race is secured to the ring 9| `by cap screws 94.

The roller bearings 88 and89constitute inboard bearing means which rotatably mount the axle shaft 81 on the transmission housing 1, and these bearings also function to secure the axle shaft 81 against axial displacement relative to the transmission'housing, axial thruston the shafttoward the right being taken 11p-by theA roller' bearing 88, andaxial thrust toward the leftbeing taken up byv the roller bearing 89. Adjustment of the roller bearings 88 and 89 to provide for rotation of the shaft 81 without appreciable-radial and axial play is effected by shims 9B between the ring 9| and the retainer 93.

The spur gear 86 is connected with the shaft 0l in non-rotatable but axially separable' relation. As indicated in Fig. 2, the hub of the geai` 80 has axial splines which cooperate with corre,-

spending axial splines 85 of the shaft 81 to secure the gear and shaft against relative rotation, and arcuate retainers 91 are secured to the gear 86 by cap screws 98 and engage a circumferential groove of the shaft 81 to releasably secure the gear and shaft in axially fixed relation to each other. A closure cap 99 is mounted in the bore of the square boss 43 and sealedby a packing |0l.

At the left side ofthe transmission housing 1 the live axle shaft 81 extends through the hubof a track belt drive sprocket |02, and into an outboard bearing which is generally indicated by the reference character |03 and which cooperates with the axle shaft 81 to rotatably connect the latter in supported relation with the track frame at the left side of the tractor, as will be `discussed in fuller detail hereinbelow. The hub of the track belt drive sprocket |02 has tapered axially extending splines in engagement With corresponding tapered axially extending splines |05 on the shaft 81, and a nut |04 is drawn up on the shaft 81 against the sprocket |02 to securely connect the sprocket and shaft in non-rotatable andaxially fixed relation to each other. A locking plate |08 for the nut 04 is securedto the hub of the sprocket |02 by screws |01.

It is desirable to maintain a supply of lubricant within the compartment 23 of the transmission housing 1 to insure proper lubrication of therela'- tively contacting teeth of the gears 84, and of the gears 12, 13, and also proper lubrication of the roller bearings 58, 81, 16, 11, 88 and 89. To this end, a cover |08, as shown in Figs. land 3, is bolted in sealed relation to the back Vplate 56 (Fig. 5) of the compartment 23 to close the aperture of said back plate, and a rotary shaft seal |09 is operatively interposed between the shaft 8E and the end Wall of the housing 1 adjacent to the sprocket |02. The aperture in the inter'- mediate wall 25 through which the pinionshaft 51 extends is closed by a seal 06, as has been mentioned hereinb'efore. The seal |09 is preferaby of the axial contacttype and may be con-v structed as disclosed,Y for instance, in U. S. 2,358,830, September 26, 1944, F. A. Schick, for' Track Roller Seal. As shown in Fig. 2, the seal |09 is operatively associated with the hub ofthe track belt drive sprocket |02 and with the retainer 93 for the roller bearing 89, the seal being surrounded in closely spaced relation by'a dirt guard and the latter being held in place by the mentioned cap screws 94.

Referring to Fig. 3, the track frame 2 at the left side of the main body i comprises an outer side channel I2, an inner side channel ||3, a suitable structure including a tubular housing |4 (Fig. 1) rigidly connected to both channels and retaining them in fixed parallel relation to each other, and a diagonal brace arm H6 lwhich is rigidly connected at its forward end to the inner side channel i i3 by a foot piece i1 and which is pivotally connected at its rear end with the main body of the tractor, as will be discussed more fully hereinbelow. A series of truck rollers IIB which bear upon the lower run of a track belt ||9 are mounted on the track frame 2 at the lower side of the latter, as indicated in Fig. 1 and a track belt supporting idler |2| is rotatably and reciprocably mounted between the side channels I |2 and H3 at the forward end of the track frame 2. The front idler |2I is backed by a conventional recoil or track release mechanism such as disclosed, for instance, in U. S. Patent 2,326,486, August 10, 1943, E. F. Norelius, Track Release Mechanism. The mentioned tubular housing H4 preferably encloses a coil spring and other parts, not shown, of the track release mechanism. Also mounted `on the housing H4 is a supporting roller |22 for the upper run of the track belt H9.

The mentioned outboard bearing |03 which, as stated, connects the live axle shaft 81 shown in Fig. 2, with the track frame 2, is mounted on the outer side channel H2 as a portion of the latter which extends rearwardly beyond the rear end of the inner side channel H3, and at the axially outer side of the nal drive sprocket |02, as generally indicated in Fig. 3. Referring to Figs. 2 and 8, a bracket comprising a base |23 and a cap |24, extends upwardly from the channel H2 at 4the axially outer side of the drive sprocket |02, the top flange and part of the web of the channel I I2 being cut out to accommodate portions of the bracket base 23. The latter is secured to the channel II2 by welding, and the connection between the base |23and the channel is reinforced by vertical webs` inside of the channel.` The cap |24 is held down on the base |23 by a pair of long vertical cap screws |21, and a semi-circular cylindrical inner surface of the cap I 24 is formed yconcentrically with a complementary semi-circular cylindrical surface of the base |23 to provide a cylindrical opening |28 (Fig. 2) at the rear end of the track frame 2 above the side channel H2.

An annular bearing cage |29 (Fig. 2) has an axially extending cylindrical portion within the cylindrical opening I 28 of the bracket 23, |24, the outside diameter of said cylindrical portion of the cage |29 closely matching the diameter of the opening |28, so that the cage will have no radial play within the opening |28 upon tightening of the screws 21 and, on the other hand, will not be distorted by such tightening of the bolts |21.

The cage |29 surrounds a portion of the live axle shaft 81 at the axially outer side of the nut |04, and a self-alining double-row roller bearing I 30 is operatively interposed between the shaft 81 and the cageY |29. The inner race of the bearing |30 abuts a shoulder |3I of the shaft 81, and a castellated nut I 32 on a threaded end portion of the shaft 81 is drawn up against said inner race and locked by a cotter pin so as to secure the inner race of the bearing |30 in axially fixed position on the shaft 81. Two outer races |33 and |34 of the roller bearing |30 are tted into the bearing cage |29, the outer race |33 abutting an internal radial ange |38 of the cage, and the outer race |34 being axially engaged by a short axially extended ring portion of a bearing cap |31. A circumferential series of relatively long cap screws |38 secure the cap |31 to the bearing cage |29, and another circumferential series of cap screws |39 secure the cap |31 to the bracket base |23 and to the bracket -cap |24. A dished .guard |4| for the track belt drive sprocket |02 is suitably secured in place at the axially outer side of the latter, preferably by means of the screws |39 which connect the bearing cap |31 to the bracket cap |24. p

From the foregoing description of the outboard bearing |03 at the axially outer side of the track belt drive sprocket |02, it will be seen that said outboard bearing compises complementary load transmitting elements, such as the inner and outer races of the self-alining, double-row roller bearing |30, which are operatively associated in axial thrust transmitting relation to each other. and which are connected, respectively, in `axial thrust transmitting relation with the axle shaft 81, and with the track frame 2.

The bearing cage |29 has an annular skirt portion in radially spaced relation to the axle shaft 81, which projects axially from the bracket |23, |24 at the inner side of the latter, and which terminates in proximity of the nut |04. The mentioned skirt portion surrounds a rotary shaft seal |42 which is operativelyinterposed between the flange |36 of the bearing cage |29 and the nut |04'on the shaft 81. The `seal |42, like the seal |09 between the sprocket |02 and the bearing retainer 93, type.

In connection with the description of the transmission housing 1, it has been pointed out hereinbefore thatl the compartment 23 for the final drive-gear train at the left side of the tractor forms an enclosure in which lubricant may be stored for maintaining the gear contacts of the final drive geartrain and the bearings in which the pinion shaft 51, the arbor 14 and the live axle shaft 81 are rotatably mounted on the housing 1, properly lubricated.` As shown in Fig. 2, the bearing cage |29 and the bearing cap |31 define a chamber, part of which is occupied by the double-row roller bearing |30, and said bearing chamber communicates with the interior of the final drive gear compartment 23 through an axial passage |43 of the live axle shaft 81, the passage |43 being formed by a central axial bore through the shaft and 'being open at both ends of the latter. `Lubricant admitted into the nal drive gear compartment 23 may therefore pass through the passage |43 into the mentioned chamber containing the double-row roller bearing |30, and the latter will therefore be automatically and 'adequately lubricated as long as a proper supply of lubricant is maintained in the final drive gear compartment 23. The rotary shaft seal |42 prevents loss of lubricant from the chamber containing the double-row roller bearing I 30. f

Designating the bearing |03 as pivot means, it will be noted that such pivot means is `mounted on and has wearing surfaces; namely, the roller con',- tacting surfaces of the inner and outer races of the roller bearing |30, outside of the transmission housing 1, and that lubricant conduit means, including the passage |43 and the cap |31; com-4 municate with the interior of the transmission housing 1 and with 'the wearing surfaces of the pivot means |03. The cage |29, the cap |31 and the seal |42 also constitute means for retaining lubricant which passes from the interior of the final drive casing 23 through the opening of the passage |43 at the axially outer end of the shaft 81,V in communication with the wearing `surfaces of the bearing |03.

In connection with the description of the track frame 2, it has been stated hereinbefore that the diagonal brace arm ||6 is pivotally connected at its rear end tothe main body I of the tractor. As indicated in Figs. 3 and 4, a pivot pin |44 which extends through an eye |46 at the rear end of the diagonal brace arm H6 is mounted at the underside of the transmission housing 1in axial alinementwith the live axle shaft V,81.

is preferably of the axial contact Welded to the underside of the bottom wall 29 of the transmission housing 1, and at the axially inner side of the eye |46 is a block |41 which has a semi-cylindrical recess lfor the reception Vof the pivot pin 44, and a cap |48 having a similar semi-cylindrical recess is bolted to the block |41 and bears upon the pin |44 to mount the latter at its left end on the transmission housing 1. At its right end, the pin |44 is similarly mounted by means of a block |49 and a cap ISI, as indicated in Figs. 3 and 4, and as more clearly shown in Fig.

From the foregoing explanations it will be apparent that the herein disclosed embodiment of the invention incorporates a live axle structure as represented by the shaft 81; outboard bearingmeans comprising a radially outer element as represented by the bracket assembly |23, |24, which is rigidly secured to the frame of the track unit 2, and a radially inner element as represented by the axially outer end portion of the shaft 81. The radially inner element of the outboard bearing means is rotatable in unison with the live axle shaft and associated, independently ofthe tractor main body, in radial load transmitting relation with the radially outer element of the outboard bearing means, whereby rearward thrust loads upon the track frame will be taken up at the rear end of the ltrack frame side channel I2, that is, at the outer track frame mounting arm, entirely by the outboard bearing means. A pair of axially spaced inboard bearings, as represented by the roller bearings 88 and 89 rotatably mount the live axle structure at the axially inner side of the track belt drive sprocket |02 on the tractor main body. A nal drive gear, as represented by the gear 86, is fixedl'y secured to the live axle shaft in the space between the inboard bearings; and another nal drive gear, as represented by the gear 84, is rotatably mounted on the tractor main body and has teeth in mesh with the rst mentioned final drive gear 86. The diagonal brace arm IIB and its pivotal `mounting on the main frame by means of the pivot pin |44 provide a connection between the main body and the frame of the track unit 2 independent of the outboard bearing |03 but operative in coniunction with the outboard bearing |03, to stabilize said track frame against toeing in and out and against i lateral' tilting relative to the main body.

The track belt drive mechanism and the track frame mounting which have been explained hereinbefore with reference to the left side of the tractor shown in Figs. l, 3 and 4, are substantially duplicated at the right side of the tractor. That is, the nal drive gear compartment 24 at the right end of the transmission housing 1 corresponds as to its details of construction to the iinal drive gear compartment 23, and it encloses a iinal drive gear train which is arranged in driven relation with the steering clutch 22 but is otherwise a substantial duplicate or the unal drive gear train which is arranged in driven relation with the steering clutch 2| at the left side of the tractor, duplicate parts at opposite sides of the tractor being designated in Figs. 3 and 4 bythe same reference characters. Similarly, the track frame 3 atv the right side of the tractor is constructed inA substantially the same manner as the track frame 2 at the left side, and the explanations hereinabove with respect to the mounting of the track frame 2 on the main body 'similarly apply to the mounting of the track frame 3, the same reference characters being sprocket 12 used in Figs. 3 and 4 to designate duplicate parts with reference to the construction and mounting of the self-laying track mechanisms at opposite sides oi the tractor.

A forward load supporting connection between the main frame i and the track frames 2 and 3, comprises a transverse leaf spring |52 which, as shown in Fig. 3, is pivoted intermediate its ends on the main body I at |53, and which has opposite end portions bearing loosely upon top portions of the track -frames 2 and 3. Generally, the leaf spring |52 serves the same purpose and performs the same function as the transverse leaf spring in a conventional tractor of the three-point suspension type. That is, the spring |52 provides a forward or rst suspension point, at |3, for the main frame, and it is rockable reiative to the main frame so as to accommodate up and down swinging movement of the track frames about the axis ofy rotation of the track belt drive sprockets |02. The outboard bearing |03 which is associated with the live axle S1 at the leit side of the tractor, is operative to pivotally support the main body, at a second suspension point, on the track frame 2,V and the outboard bearing |03 which is associated with the live axle 31 at the right side of the tractor, is operative to pivotally support the main body, at a third suspension point, on the track yframe 3. In this connection, it should be noted that the sprocket wheels |02 are so proportioned, in conformity with well-known principles, thatl they are normally relieved from the function of sustaining part oi the weight of the main body on the track belts, such proportioning of the track belt drive sprocket |02 at the left side of the tractor being indicated in Fig. 1 by a slight upward and rearward slope of the lower run of the track belt in proximity to the track belt drive IZ. The diagonal brace arm I|6 of the left track frame is eiective, in conjunction with the outboard bearing |03 at the left side of the tractor, to stabilize said track framn against toeing in and out and against lateral tilting about the hereinabove mentioned second suspension point, and the diagonal brace arm IIi of the right track `frame 3 is similarly effective, in conjunction with the outboard'bearing |03 at the right side of the tractor, to stabilize the right track frame against toeing in and out and against lateral tilting about the hereinabove mentioned third suspension.

The construction of the transmission housing i as an integral unit in the manner described hereinbefore provides for accurate alinement of the inboard bearing 38 with the inboard bearing 88, and similarly for accurate alinement of the bearing 16 with the bearing 11 and of the bearing 55 with the bearing 61. Such accurate bearing alinement is obtained by machining the seats for each pair ci coaxial bearings on the intermediate wall 26 and on the left end wall, after these walls have been permanently united with each other through the circumferential wall 41 and other members, as has been explained hereinbefore. Due to the integral construction of the transmission housing, it is further possible to position,

and maintain the axis of the bearings 16, 11 in highly accurate transversely spaced relation to the axis of the bearings 88, 89 and to position and maintain the axis of the bearings 58 and 51 in highly accurate transversely spaced relation to the axis of the bearings 16 and 11.

For purposes of assembly, the pinion shaft 51 with the pinion 12 may be moved axially into the 13 nal drive gear compartment through the registering openings of the intermediate housing wall or partition 26 and of the annular boss 44, prior to the installation of the roller bearing 58 in the annular boss 44. 13 may be installed by first moving it into the space between the walls 26 and 49 through the aperture of the back plate 56, and by then moving the arbor. 14 axially through the registering openings of the end plate 49 and ring 82. While the arbor 14 is axially moved into the nal drive gear compartment, the gear 13 may be held by hand in the proper position for engagement with the splines 15 of the arbor 14, and after the bearing 11 and cap 8| have been installed, the gear 13 may be secured by means of the retainers 18, the cap screws 19 being accessible through the opening of the back plate 56. The procedure of installing the gear 85 is similar to that of installing the gear 13. That is, the gear 86 is irst moved into the iinal drive gear compartment through the opening of the back plate 56, and the axle shaft 81 is then passed axially through the 4 ring 9| and through the hub of the gear 86 to engage the axial splines 85 of the shaft 81 with the corresponding axial splines of the gear 86. The remaining operations for positioning and securing the shaft 81 and the gear 86 in desired relation with respect to the housing 1 may then be performed without difficulty, as will be ap-` 1' parent from Fig. 2. The cap screws 98 for the retainers 91, like the cap screws 19 for theretainers 18, are accessiblethrough the aperture of the back plate 56.

Steering of the tractor is effected, in the usual turn, suitable brake mechanism, not shown. be-

ing associated for that purpose with the steering clutches in conformity with well-known and generally accepted principles. While a turn is made, say to the right, a strong lateral thrust force in the direction of arrow |54 in Fig. 3 becomes eective upon the track frame 2 and tends to swing the latter away from the rcain bodv I, with the result that a rearward horizontal thrust in the direction of arrow |56 in Fig. 3 becomes eiective upon the outer end of the live axle shaft 81 which is journaled in the outboard bearing |03 at therear end of the track frame 2. During the assumed right-hand turn of the tractor, the track belt drive sprocket |02 at' the left side of the tractor is driven by the engine 4 in the direction of arrow |51 in Fig. 1, andthe arrow |58 in Fig. 3 indicates the direction in which the sprocket |02 exerts a horizontal thrust upon the live axle 81 at the left side of the tractor while the tractor is being turned to the rightv and a backward thrust is exerted, as pointed out hereinbefore, upon the outer end of the same live axle 81 through the track frame 2.

It will be noted that the horizontal thrust forces indicated by the arrows |55 and |58 in Fig. 3 act upon the live axle shaft 81 horizontally in opposite directions and outside of the transmission housing 1. Under these conditions, the inboard bearings 88 and 89 for the live axle-,shaft 81 at the left side of the tractor, and particularly the inboard bearing 89 next to the track' belt drive sprocket |02. are not apt to become unduly loaded during a right-hand turn of the tractor. More particularly, the inboard bearing 89 next to the track belt drive sprocket |02 at the left side of they tractor is not apt to become loaded.V to

The intermediate spur gear such an extent as to set up internal stresses in the transmission housing 1 which would objectionably disturb the highly accurate bearing alinement and the highly accurate gear spacing which are necessary for elicient and trouble-free operation of the final drive gear train under heavy loads.

The foregoing considerations of the eiect of a righthand turn uponthe live axle shaft 81 at the left side of the tractor are analogously applicable to the live axle shaft 81 at the right side of the tractor in case of a left-hand turn. That is, when the tractor executes a turn to the left, the backward force on the outer side channel ||2 of the right track frame is counteracted by the driving thrust of the track belt drive spocket |02 at the right side of the tractor, with the result that the inboard bearing next to the right track belt drive sprocket is relieved from undue loads.

Each of the self-laying track mechanisms at the opposite sides of the tractor includes, as stated hereinbefore, a track release mechanism, the one at the left side being generally indicated in Fig. l, by the reference character |50 and as shown in said igure being operatively interposed between the track frame 2 and the front idler 2 Should a rock or other solid obstruction become lodged on thelower run of the track belt H9, continued rotation of the sprocket |02 which drives said track belt in the direction of arrow |51 may force the rock to pass with the track belt around the track belt drive sprocket. In that case the front idler |'2| isforced back against the `resistance of the track release mechanism |59,

and the tension of the track belt |9 increases considerably beyond normal. Under these conditions the track frame 2 will again exert a heavy horizontal thrust upon the outer end of the live axle shaft 81, in the direction of arrow |56 in Fig. 3, and the left track belt drive sprocket |02 will exert a heavy horizontal thrust upon. the live axle 81 in the opposite direction as indicated by the arrow |58. Due to the proximity of the left outboard bearing |03 to the left track belt drive sprocket |02 a maior part of the horizontal thrust upon the axle shaft 81 in the direction of arrow |55 is balanced bv the counterthrust of the left track belt drive Sproc"et |02. In other words, a maior part of the relatively opposing forces is neutralized outside and independently of the transmission housing 1, and consequently, the latter is not apt to be unduly stressed so as to objectionablv disturb the mentioned highly accurate relation between the relatively movable elements of the final drive gear train at the left` side of the tractor when the tension of the track belt at said side of the tractor increases considerably beyond normal and to the point where the track release mechanism |59 becomes operative. The same conditions prevail with reference to the iinal drive gear train at the right side of the tractor when the right track release mechanism is forced to operate.

One of the most common operations for which crawler tractors are used is to push'earth moving and similar eouipment. and it is usual to attach such eouipment. particularly bulldozers, in thrust transmitting relation directly to the track frames rather than to the main body of the tractor. Referring to Fig. 3, the push arms of a bulldozer are indicated in dash-dotted lines at opposite sides of the tractor and designated 4by the reference characters |5| and |62. For purposes of attaching the bulldozer arm |G| in thrust transmitting reation to the track frame 2, a mounting 'bracket |63, which is shown in section in Fig. 9, may be secured to the side channel I2 of the track frame 2 somewhat ahead of the live axle 8'? at the left side of the tractor, as generally indicated in Fig. 3. The mounting bracket |83 has a stubby extenn sion at its outer side, and a spherical surface li is formed on said extension to provide the ball part of a ball and socket connection between the bracket |68 and the bulldozer arm ifi. As indicated in Fig. 3, the connection between the bulldezer arm it! and the track frame 2 is duplicated at the right side of the tractor to secure the bulldozer arm i552 in thrust transmitting relation directly to the trackframe 3.

Referring to the force diagram shown in Fig. 10, the load condition to which the inboard bearing 89 next to the track belt drive sprocket iii? at either side of the tractor becomes subjected during bulldozing, may be analyzed as follows; The relatively opposed horizontal force components D and S represent, respectively, the reaction between the bearing 89 and its associated live axle shaft S7 due to the rearwardly directed thrust load upon the bulldozer arm at the respective side of the tractor, and the reaction between the same bearing and shaft due to the sprocket effort, that is, the tangential load on the pitch circle of the track belt drive sprocket.

The force component T'represents the reaction between the bearing 89 and its associated live axle shaft 8l due to the tooth load at the point of mesh between the gears 85| and S6 of the final drive gear train at the respective side of the tractor'. The direction of the component T is determined by the location of the gear 34 circumferentially of the gear 816 and by the proleA of vthe intermeshing teeth. The angle between the components T and S as shown in Fig. 10 is based upon a circumferential positioning of the gear 84 relative to the gear 86 substantially as shown in Fig. l and upon a standard tooth prole.

The component W represents the reaction between the bearing 89 and its associated axle shaft 81 due to that part of the weight of the main body which must be sustained by the axle shaft at the respective side of the tractor.

For purroses of exemplification, the vectors D, S, T and W in Fig. 10 may be considered to represent the following loads, based on practical observations:

D=25,200 lbs. S=17,500 lbs. T =19,700 lbs. W=10,000 lbs.

The geometrical sum of the vectors S and T is represented in Fig. 10 by the vector R-I, and the sum of the vectors R-l and D is represented by the vector R-2. Finally, the sum of the vectors R-2 and W is represented in Fig. 'l0 by the vector R-3. It will be observed that the vector R-S is relatively short, and it represents a relatively light load which, according to the hereinabove assumed figures for the components D, S, T and W, amounts to about 11,000 lbs. That means that when the tractor is pushing a bulldozer or similar earth moving equipment which is connected in thrust transmitting relation to the track zii) frames, the inboard bearings adjacent to the track Y belt drive sprockets at opposite sides of the tractor, and the transmission housing l are not apt to become loaded to such an extent as to set up internal stresses lin the transmission housing 'l which would objectionably disturb the highly accurate bearing alinement and the highly accurate gear spacing which are necessary for eificient 16 and trouble-free operation of thenal drive gear trains under heavy loads.

lReferring again to Fig. 3, it will 'be noted that the track frames 2 and 3 are not only constructed to eiciently withstand heavy loads without twisting or bending but that the eye |46 and the outboard bearing |03 of each track frame are spaced l a relatively great distance from each other, transversely or the tractor, which is a desirable feature because it provides for satisfactory stability of 'the track frames against toeing in and out and against lateral tilting relative to the mainframe.

From. Fig. 2, it will be noted that the diameter of the rotary shaft seals which are required to retain lubricant in the nal drive housings, are relatively small, which is a desirable feature not only from an engineering standpoint but also from a cost standpoint.

It will further be noted from Fig. 4 that the depending portions of the final drive housings 23 and 2li and the track belt drive sprockets |02 adjacent thereto, are arranged in relatively close proximity to each other, at each side ofthe tractor, which is a further desirable feature because it provides for maximum transverse clearance under the transmission housing 1.

In general terms, the improved crawler tractor disclosed herein comprises a unitary housing structure forming part of the tractor main body and having downwardly extended final drive gear enclosures at its opposite sides, respectively; such unitary housing structure being represented in the illustrated embodiment of the invention by the transmission housing A depending final drive gear enclosure is formed at the left side of the housing 'l by the left intermediate wall 26, the left end plate 49, the wall members all, 52, 53 and 54, back plate 56 and cover |08; and another depending nal drive gear enclosure is similarly formed at the right side of the housing 1, as explained hereinbefore.

The improved tractor further comprises a sprocket wheel, a shaft element and a pair of inboard bearings rotatably mounting said shaft element at axially spaced points thereof on a lower portion of one of said final drive gear enclosures; such sprocket wheel, shaft element and inboard bearings being represented in the illustrated embodiment of the invention by the sprocket wheel |02, shaft 81, and bearings 88, 89, at either side .of the tractor.

Power transmitting means include a lower gear, as represented by the gear 86, which is nonrotatably connected within said one final drive gear enclosure, with said shaft element-between said inboard bearings; an upper gear, as represented by the gear cluster 13, 84, which is rotatably mounted within said one final vdrive gear enclosure and which has teeth, in the present instance the teeth of gear l81|, in mesh with teeth of said lower gear; and a drive pinion, as represented by the pinion T2, which is rotatably mounted within said one final drive gear enclosure and which has teeth in mesh with teeth, in the present instance the teeth of the gear 13., of said upper gear.

A rigid track frame has two mounting arms,

lone for connection with said sprocket wheel and nel ||2, and by the diagonal brace arm IIS.

Meansindependent of the aforesaid housing structure rotatably connect said one mounting arm of the track frame in radial load transmitting relation with said sprocket wheel, such independent means being represented in the illustrated embodiment of the invention by the outer end of the shaft 8l and the outboard bearing |03.

Pivot means operatively connect the aforesaid other arm of the track frame with the unitary housing structure intermediate the nal drive gear enclosures, such pivot means being represented in the illustrated embodiment of the invention by a pivot pin |44 and bracket structures |41, |48, |49, as shown in Figs. 3 and 5. An endless track belt is operatively mounted on the aforesaid sprocket wheel and track frame, such arrangement of the track belt in the illustrated embodiment of the invention being shown in Fig. 1.

It should be understood that it is not intended to limit the invention to the particular forms and details described hereinabove and that the invention includes such other forms and modications as are embraced by the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a crawler tractor, the combination of, a unitary housing structure forming part of the tractor main body and having downwardly extended final drive gear enclosures at its opposite sides, respectively; a sprocket wheel; an axle structure fixedly secured to said sprocket wheel; a pair of axially spaced inboard bearings rotatably mounting said axle structure on a lower portion of one of said final drive gear enclosures; power transmitting means including a lower gear within said one nal drive gear enclosure and nxedly secured to said axle structure between said inboard bearings, and an upper gear rotatably mounted within said one nal drive gear enclosure and having teeth in mesh with teeth of said lower gear; a rigid track frame having two mounting arms, one for connection with said axle structure and the other for connection with said housing structure; outboard bearing means comprising a radially outer element rigidly secured to said one mounting arm, and a radially inner element rotatable in unison with said axle structure and associated, independently of said main body, in radial load transmitting relation with said radially outer element, whereby rearward thrust loads upon said track frame will be taken up at said one mounting arm entirely by said outboard bearing means; pivot means operatively connecting said other mounting arm with said housing structure intermediate said final drive gear enclosures; and an endless track belt operatively mounted on said sprocket wheel and track frame.

2. In a crawler tractor, the combination set forth in claim 1, and in which said power transmitting means further include a drive pinion rotatably mounted within said one final drive gear enclosure, a gear cluster having two gear sections, one in mesh with said drive pinion and the other forming said upper gear, and bearing means rotatably mounting said gear cluster within said one final drive gear enclosure.

3. In a crawler tractor, the combination of a main body, a live axle structure, a track belt drive sprocket xedly secured to an intermediate portion of said live axle structure; a pair of axially spaced inboard bearings rotatably mounting said axle structure, at the axially inner side of said track belt drive sprocket, on said main body; a track frame having a mounting arm at the axially outer side ofsaid track belt drive sprocket; outboard bearing means comprising a radially outer element rigidly secured to said mounting arm, and a radially inner element rotatable in unison with said axle structure and associated, independently of said main body, in radial load transmitting relation with said radially outer element, whereby rearward thrust loads upon said track frame will be taken up at said mounting arm entirely by said outboard bearing means; load transmitting means operatively interposed between said main body and track frame for stabilizing said track frame against toeing in and out and against lateral tilting relative to said main body; a final drive gear xedly secured to said axle structure in the space between said inboard bearings; and another nal drive gear rotatably mounted on said main body and having teeth in mesh with said rst mentioned final drive gear.

WILLIAM F. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,815,339 Turzicky July 21, 1931 1,865,133 Osman June 28, 1932 2,002,474 Johnston et al. May 21, 1935 2,054,782 Day Sept. 15, 1936 2,076,009 Starr et al. Apr. 6, 1937 2,146,168 Baker et al. Feb. 7, 1939 2,146,882 Baker et al. Feb.. 14, 1939 2,156,565 Johnston et al. May 2, 1939 2,190,254 Caproni Feb. 13, 1940 2,225,233 Rogers et al. Dec. 17, 1940 2,297,485 Lentz Sept. 29, 1942 2,389,624 Knox et a1. Nov. 27, 1945 2,453,360 Burks Nov. 9, 1948 

